1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly to a plasma display panel that is adaptive for preventing mis-discharge from being generated in adjacent cells in driving the PDP and for improving picture quality.
2. Description of the Related Art
Recently, there have been developed various flat display panels that can reduce their weight and bulk, which was the disadvantage of a cathode ray tube CRT. Such flat display panels include liquid crystal displays LCD, field emission displays FED, plasma display panels PDP, electro-luminescence EL display device and so on.
The PDP among these display devices takes advantage of gas discharge and has an advantage of being made into a large-dimensioned panel easily. A three-electrode AC surface discharge PDP is a typical PDP, which includes three electrodes as shown in FIG. 1 and is driven with AC voltage.
Referring to FIG. 1, a discharge cell of a three-electrode AC surface discharge PDP in the related art includes a first electrode 12Y and a second electrode 12Z formed on an upper substrate 10, and an address electrode 20X formed on a lower substrate 18.
The first and second electrodes 12Y and 12Z are formed of a transparent material in order to transmit the light supplied from the discharge cell. There are formed bus electrodes 13Y and 13Z of a metal material in parallel to and on the rear surface of the first and second electrodes 12Y and 12Z. Such bus electrodes 13Y and 13Z are used to supply driving signals to the first and second electrodes 12Y and 12Z that have high resistance.
There are formed an upper dielectric layer 14 and a passivation film 16 on the upper substrate 10 provided with the first and second electrodes 12Y and 12Z. On the upper dielectric layer 14, there are formed wall charges generated upon plasma discharge. The passivation film 16 prevents the damage of the upper dielectric layer 14 by the sputtering generated upon the plasma discharge, and at the same time, increase the emission efficiency of secondary electrons. The passivation film 16 is usually magnesium oxide MgO.
There are formed a lower dielectric layer 22 and barrier ribs 24 on the lower substrate 18 provided with the address electrode 20X, and the surface of the lower dielectric layer 22 and the barrier ribs 24 is coated with a phosphorus 26. The address electrode 20X is formed crossing the first and second electrode 12Y and 12Z. The barrier ribs 24 are formed parallel to the address electrode 20X to prevent an ultraviolet ray and a visible ray from leaking out to adjacent discharge cells, wherein the ultraviolet ray and the visible ray are generated by discharge.
The phosphorus 26 is excited by the ultraviolet ray generated upon the plasma discharge to generate any one of red, green and blue visible rays. There is injected an inert mixture gas such as He+Ne, He+Xe or He+Ne+Xe for the gas discharge in a discharge space provided between the upper/lower substrates and barrier ribs.
In the related art PDP, the first and second electrodes are formed opposite to each other in each discharge cell as in FIG. 2. The first electrode 12Y is supplied with reset pulses, scan pulses and first sustain pulses. The second electrode 12Z is supplied with second sustain pulses.
The discharge cells are initialized when the reset pulse is applied to the first electrode 12Y. The address electrode 20X is supplied with data pulses synchronized with the scan pulses when the scan pulses are applied to the first electrode 12Y. At this moment, there occur the address discharges in the discharge cells supplied with the scan pulses and the data pulses.
The first and second sustain pulses are alternately applied to the first and second electrodes 12Y and 12Z after the address discharges being generated in the discharge cells. If the first and second sustain pulses are applied to the first electrode 12Y and the second electrode 12Z, there is generated sustain discharges in the discharge cells where the address discharges were generated. The discharge time of the sustain discharge is determined by a gray level value, and accordingly a picture is displayed in accordance with gray level values.
On the other hand, in the related art PDP, the first and second electrodes 12Y and 12Z are formed opposite to each other with wide areas in each of the discharge cells. In this way, if the first and second electrodes 12Y and 12Z are wide in area, a lot of power is dissipated, and accordingly the discharge efficiency of the PDP is deteriorated. In order to overcome such a disadvantage, there has been suggested a PDP as in FIG. 3.
Referring to FIG. 3, a PDP according to another embodiment of the related art has a delta type structure where discharge cells located adjacent to each other on the upward/downward each make up one pixel. In other words, in the PDP according to the embodiment of the related art, an R sub-pixel and a B sub-pixel located in the nth (n is a natural number over 1) line and a G sub-pixel located in the (n+1)th or (n−1)th line make up one pixel.
The PDP according to the embodiment of the related art includes an address electrode 40X, a first and a second electrode 32Y, 32Z formed crossing the address electrode 40X, and a first and a second bus electrode 33Y, 33Z formed on the first and second electrodes 32Y and 32Z.
The first and second electrodes 32Y, 32Z include a first and a second main electrode 32A, 32C formed in a perpendicular direction to the address electrode 40X, and a first and a second auxiliary electrode 32B, 32D extended from the first and second main electrodes 32A, 32C in the same direction as the address electrode 40X.
The first auxiliary electrode 32B is formed on both sides of the first main electrode 32A, and the second auxiliary electrode 32D is formed on both sides of the second main electrode 32C in the same way as the first auxiliary electrode 32B.
The address electrode 40X includes an address main electrode 40A formed in a line crossing the first and second main electrodes 32A, 32C, and an address auxiliary electrode 40B extended by a designated width in a direction of crossing the address main electrode 40A within a discharge cell that makes up one pixel.
Further, on the upper surface of the POP according to another embodiment of the related art, there are the second auxiliary electrodes 32B alternately extended from the first main electrode 32A, and a first dielectric layer 44B that the upper dielectric layer and the protective film are sequentially deposited on the entire upper plate to cover the second auxiliary electrode 32B.
The wall charges generated upon the plasma discharge are accumulated through the upper dielectric layer on the first dielectric layer 44B, which prevents the damage of itself caused by the sputtering generated upon the plasma discharge by way of the passivation film and at the same time increases the emission efficiency of the secondary electrons.
On the lower surface of the PDP, there are formed a first to a third address electrode 42A, 42B, 42C crossing the first and second electrodes 32Y and 32Z, a second dielectric layer 44a on the entire lower plate to cover the address electrodes 42A, 42B, 42C, and horizontal barrier ribs 46B on the lower surface in the same direction as the first to third address electrodes 42A, 42B, 42C. There is formed a phosphorus (not shown) on the surface of the second dielectric layer 44A and the horizontal barrier ribs 46B. The first and third address electrodes 42A, 42C formed on both sides among the first to third address electrodes 42A, 42B, 42C are the address auxiliary electrode 40B extended from the address main electrode 40A to the direction of the first and second electrodes 32Y, 32Z, and the second address electrode 42B is the address electrode main electrode 40A. The barrier ribs 46B are formed parallel to the first to third address electrodes 42A, 42B, 42C to prevent the ultraviolet ray and the visible ray generated by the discharge from leaking out to the adjacent discharge cells.
In the PDP according to the embodiment of the related art, the upper part of the barrier ribs 46 has a rectangular shape.
FIGS. 5 to 12 are views representing equipotential surfaces when a specific voltage is applied to a discharge cell according to the POP shown in FIG. 4.
Referring to FIGS. 5 to 12, the width of the second auxiliary electrodes 32B formed on the upper plate of the PDP is 185 μm, the width of the first and second address electrodes 42A, 42C formed on both sides of the lower plate is 150 μm. 70 μm is the width of the second address electrode 42B, which is formed between the first and third address electrodes 42A, 42C and where the address auxiliary electrode 40B is not formed. 120 μm is the height of the horizontal barrier ribs 46B formed being closed on the lower plate, and the dielectric constant of the horizontal barrier ribs 46B is 12. At this moment, the second auxiliary electrodes 32B consist of a first-second auxiliary electrode 32B1 formed on its left on the basis of the horizontal barrier ribs 46B, and a second—second auxiliary electrode 32B2 formed on its right.
Further, in FIGS. 5 to 12, if the voltage applied is 0V, no voltage is applied, 1V means that a designated voltage is applied, and −1.2V means that a reverse voltage is applied and the absolute value of the voltage is higher than 1V.
Referring to FIGS. 5 to 7, the first-second auxiliary electrode 32B1 and the first and third address electrodes 42A and 42C of the PDP are supplied with 0V, i.e., no voltage is applied, and a voltage of 1V is applied only to the second address electrode 42B. At this moment, the discharge cell including the first and third address electrode 42A and 42C is a turned-off cell (hereinafter, off-cell), if such an off-cell is turned on, it is considered that there occurs mis-discharge.
Comparing FIG. 5 with FIG. 6, if the second address electrode 42B is supplied with a data voltage, the maximum electric field (the maximum electric field is formed between the upper part of the barrier ribs 66 and the first dielectric layer) of the off-cell including the first and third address electrodes 42A, 42C has a higher value in the event of FIG. 6 (Emax=1.55E-2) where an air gap exists between the horizontal barrier ribs 46B and the first dielectric layer 44B than in the event of FIG. 5 (Emax=8.8E-3) where an air gap does not exist. Hereby, there is a higher probability in mis-discharge in the event that there is the air gap between the horizontal barrier ribs 46B and the first dielectric layer 44B.
FIG. 7 represents the case that the air gap is big between the horizontal barrier ribs 46B and the first dielectric layer 44B. At this moment, the maximum electric field of the off-cell in FIG. 7 (Emax=1.48E-2) is not changed much when comparing with FIG. 6 (Emax=1.55E-2). In FIG. 7, the direction of the electric field is a perpendicular direction to the equipotential surfaces formed between the horizontal barrier ribs 46B and the first dielectric layer 44A. In this case, the electric field in the air gap (I) causes charged particles to move upward or downward in accordance with their polarity.
Referring to FIGS. 6 and 7, the first-second auxiliary electrode 32B1, the second-second auxiliary electrode 32B2 and the third address electrode 42C of the PDP are supplied with 0V, i.e., no voltage is applied, and a data voltage of 1V is applied to the first and second address electrodes 42A and 42B, FIG. 6 represents the case that there is no air gap between the horizontal barrier ribs 46B and the first dielectric layer 44B, and FIG. 7 represents the case that there is air gap between the horizontal barrier ribs 46B and the first dielectric layer 44B.
When comparing the strength of the maximum electric field induced to the off-cell including the third address electrode 42C in FIG. 6 with that in FIG. 7, as can be seen in FIGS. 3 and 4, the strength of the electric field is higher in FIG. 7, i.e., when there is air gap (Emax=1.48E-2), than when there is no air gap (Emax=8.85E-3).
Referring to FIGS. 8 and 9, the first-second auxiliary electrode 32B1, the second-second auxiliary electrode 32B2 and the third address electrode 42C of the PDP are supplied with 0V, i.e., no voltage is applied, and a data voltage of 1V is applied to the first and second address electrodes 42A and 42B. FIG. 8 represents equipotential surfaces when there is no air gap between the horizontal barrier ribs 46B and the first dielectric layer 44B, and about 9.02E-3 is the strength of the maximum electric field Emax induced to the off-cell that includes the third address electrode 42C. FIG. 9 represents equipotential surfaces when 25 μm is the air gap between the horizontal barrier ribs 46B and the first dielectric layer 44B, and about 1.52E-2 is the strength of the maximum electric field Emax induced to the off-cell that includes the third address electrode 42C.
Referring to FIG. 10, the first-second auxiliary electrode 32B1, the second-second auxiliary electrode 32B2 and the second and third address electrodes 42B, 42C of the PDP are supplied with 0V, i.e., no voltage is applied, and a data voltage of 1V is applied only to the first address electrode 42A. In this case, FIG. 10 represents equipotential surfaces when there is no air gap between the horizontal barrier ribs 46B and the first dielectric layer 44B, and about 9.4E-3 is the strength of the maximum electric field Emax induced to the off-cell that includes the third address electrode 42C.
As can be seen in FIGS. 5 to 9, the presence or absence of the air gap between the horizontal barrier ribs 46B and the first dielectric layer 44B is an important factor with respect to the mis-discharge. In other words, the strength of the maximum electric field is high when there is the air gap. Further, it can be seen through FIGS. 6 and 7 that the strength of the maximum electric field in the vicinity of the air gap is not much changed in accordance with the size of the air gap.
When observing though FIGS. 6, 7 and 9, cross talks occur because the voltage applied to the second address electrode 42B located at the lower part of the horizontal barrier ribs 46B forms a strong electric field in the vicinity of the air gap within the discharge cell if there is the air gap between the horizontal barrier ribs 46B and the first dielectric layer 44B. Comparing FIG. 8 with FIG. 10, there is generated no cross talk when 0V voltage is applied to the second address electrode 42B formed at the lower part of the horizontal barrier ribs 46B.
FIG. 11 represents equipotential surfaces when a specific voltage is applied to a discharge cell in accordance with the related art.
Referring to FIG. 11, the first-second auxiliary electrode 32B1, the second—second auxiliary electrode 32B2 of the POP are supplied with −1.2V voltage, the third address electrode 42C are supplied with 0V, and a data voltage of 1V is applied to the first and second address electrode 42A, 42B. In this case, the discharge cell including the first address electrode 42A is turned on (hereinafter, on-cell), and the cell including the third address electrode 42C is the off-cell because the data voltage is not applied. Further, FIG. 11 represents equipotential surfaces when 5 μm is the air gap between the horizontal barrier ribs 46B and the first dielectric layer 44B.
FIG. 12 is a diagram representing the relative strength of the electric field formed within the right and left discharge cells.
Referring to FIG. 12, the strength of the maximum electric field in the off-cell including the third address electrode 42C in the PDP appears to be almost the same as the strength of the maximum electric field of the discharge cells where the data voltage is applied to the first address electrode 42A when there is the air gap between the horizontal barrier ribs 46B and the first dielectric layer 44B as shown in FIG. 11, and the upper part of the horizontal barrier ribs 46B has a rectangular shape. In this case, there is a higher probability of the off-cell being turned on, i.e., a strong electric field is formed around the peripheral air gap due to the pulse applied to the column electrode of the peripheral off-cell to cause undesired discharge to be generated, thus a picture quality is deteriorated.